Polyphenols microwave assisted extraction from waste grape skins

The present work evaluated the use of Microwave Assisted Extraction (MAE) for the recovery of phenolic compounds from waste grape marc. MAE was carried out with 60% aqueous ethanol, investigating the effect of different microwave irradiation powers and times on the total polyphenols content and antioxidant power of the extracts. Process parameters of heating rate and boiling time were established for each irradiation power. MW power did not significantly influence the total phenols (TP) yield. Compared to conventional Solid Liquid Extraction, MAE reduced extraction time from 2 hours to 100 sec, achieving an equivalent TP yield (8.0±0.2 mg GAE/g grape skins). Antioxidant power of MAE extracts was slightly lower (2-10%) than SLE extracts probably due to thermal degradation